Quadtree Terrain Data Compression Using Distance-Based Pruning

2. The apparatus of claim 1 wherein the predetermined accuracy requirements specify a vertical accuracy that depends on distance from a runway.

3. The apparatus of claim 1 wherein the tree data structure is a quadtree data structure and the nested polygons are squares.

4. The apparatus of claim 1 wherein the node point of each polygon corresponds to a predetermined corner of the polygon.

5. The apparatus of claim 1 wherein the tree data structure has at least three layers of parent-child relationship.

6. The apparatus of claim 1 wherein only leaf nodes store height values.

7. The apparatus of claim 1 wherein the stored height values are represented in increments of a predetermined minimum vertical resolution.

8. The apparatus of claim 1 wherein the tree data structure is initially stored in memory using leaf nodes sized to represent a terrain grid of dimensions about 0.86 arcseconds by 0.86 arcseconds.

10. The method of claim 9 wherein the predetermined accuracy requirements specify a vertical accuracy that depends on distance from a runway.

11. The method of claim 9 wherein the wherein the tree data structure is a quadtree data structure and the nested polygons are squares.

12. The method of claim 9 wherein the node point of each polygon corresponds to a predetermined corner of the polygon.

13. The method of claim 9 wherein the tree data structure has at least three layers of parent-child relationship.

14. The method of claim 9 wherein only leaf nodes store height values.

15. The method of claim 9 wherein the stored height values are represented in increments of a predetermined minimum vertical resolution.

16. The method of claim 9 further comprising initially populating the leaf nodes using terrain height data captured from a satellite in orbit around the Earth.

17. The method of claim 9 wherein the distance calculation is performed by providing an initial set of aircraft runway location data and by culling the initial set to eliminate data for runways that are not useable for a predetermined class of aircraft.